In engine systems, the accurate detection of fuel pump solenoid closure or closing point detection for each of the cylinders of the engine is desirable to provide accurate timing of injection of fuel and control of combustion, emissions, smooth regulation of engine speed, and fuel efficiency. Prior art system and methods for detecting fuel injection solenoid closure involve detecting the change of slope of the solenoid current within a window, as the current is reduced from peak pull-in current, to hold current. However, prior art systems are susceptible to variations due to cable lengths between engine control unit and the engine cylinder solenoids, aging, ambient conditions, fuel pumps, and engine speed. Moreover, the location and the characteristic signature of such a detection scheme may vary as a function of pump, impedance of electronics/cabling/solenoid, power supply voltage, engine speed, hydraulic fuel pressure, cam location, aging, and ambient conditions. These variations reduce the reliability and accuracy of conventional methods of closing point detection.
Detecting solenoid closure in a in a fuel injection system is desirable for determining any required compensation in timing of fuel injection. The timing of fuel injection is a critical variable to control in order to achieve operational goals such as combustion quality, fuel efficiency and reduced emissions. Any inaccuracies in closing point detection impact these important goals. An appropriate algorithm with consistent detection and accuracy helps achieve these goals.
Therefore, there is a need for an improved method of detection of closing point and minimizing the susceptibility of closing point detection due to variations that change the characteristics of current waveform. The present invention provides an improved method of closing point detection by regulating the slope from peak current to the time when the closing point is detected.